Diffusion Anisotropy of the Internal Capsule and the Corona Radiata in Association with Stroke and Tumors as Measured by Diffusion-weighted MR Imaging
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AJNR Am J Neuroradiol 22:456–463, March 2001
Diffusion Anisotropy of the Internal Capsule and the
Corona Radiata in Association with Stroke and Tumors
as Measured by Diffusion-weighted MR Imaging
Shuichi Higano, Jianhui Zhong, David A. Shrier, Dean K. Shibata, Yukinori Takase, Henry Wang, and
Yuji Numaguchi
BACKGROUND AND PURPOSE: Diffusion-weighted MR images have enabled measurement
of directionality of diffusion (anisotropy) in white matter. To investigate differences in the
anisotropy for various types of pathologic findings and the association between the anisotropy
of tracts and neurologic dysfunction, we compared the anisotropy of the posterior limb of the
internal capsule and the corona radiata between patients with stroke and those with tumors
and between patients with and without hemiparesis.
METHODS: Thirty-three patients consisting of 11 with tumors and 22 with ischemic disease
(16 acute infarction, four old infarction, and two transient ischemic attack) and nine control
patients were studied with a 1.5-T MR imager. Diffusion-weighted images were obtained with
diffusion gradients applied in three orthogonal directions. The diffusion anisotropy measure-
ments were obtained from regions of interests defined within the internal capsule and the
corona radiata.
RESULTS: The diffusion anisotropy was significantly reduced in all internal capsules and
coronae radiata involved by infarcts, tumors, and peritumoral edema compared with that of
the control patients (P , .0001). This reduction was most prominent in the tracts involved by
tumors (P , .05). The anisotropy of the internal capsules and coronae radiata was significantly
decreased in cases with moderate-to-severe hemiparesis as compared with those with no or
mild hemiparesis (P , .0001). Diffusion anisotropy tended to be also reduced in normal-ap-
pearing internal capsules and coronae radiata that were remote from the involved segment of
the corticospinal tract.
CONCLUSION: The degree of impaired diffusion anisotropy may vary in different pathologic
conditions and correlate with neurologic dysfunction. The measurement of diffusion anisotropy
may provide additional information relating to neurologic function and transneuronal effects.
Diffusion-weighted imaging is a method of MR in which water diffusion rates are high and in-
imaging that is sensitive to the random motion creases in areas that have more restricted diffu-
(diffusion) of water molecules. Using specific sion. The magnitude of water diffusion (ie, the ap-
pulses (motion-probing gradients), the phase dif- parent diffusion coefficient) is known to change in
ferences between mobile protons and immobile various pathologic conditions, including ischemic
ones are accentuated (1, 2). On diffusion-weighted disease, brain tumor, and demyelinating diseases
images, therefore, MR signal decreases in regions (3–10).
In addition to the pathologic state, the water dif-
Received December 1, 1999; accepted after revision August 8, fusion is varied in normal brain tissue. In the my-
2000. elinated white matter, the water molecules move
From the Department of Radiology (S.H., J.Z., D.A.S.,
D.K.S., Y.T., H.W., Y.N.), Division of Neuroradiology, Uni-
relatively freely in the direction parallel to the fiber
versity of Rochester Medical Center, Rochester, NY. tracts but are restricted in their movement perpen-
A summary of this work was presented at the 37th Annual dicular to the tracts, which is called diffusion an-
Meeting of the American Society of Neuroradiology, San Di- isotropy (11–14). Recently, diffusion-weighted
ego, CA, April 1999. images with several different directional motion-
Address reprint requests to Yuji Numaguchi, MD, PhD, De- probing gradients have enabled evaluation of the
partment of Radiology, Division of Neuroradiology, University
of Rochester Medical Center, 601 Elmwood Avenue, Box 648,
magnitude and directionality of water diffusion (15,
Rochester, NY 14642. 16). With this technique, diffusion-weighted im-
aging has been used for investigation of white mat-
q American Society of Neuroradiology ter (eg, visualization of long fiber tracts) and for
456AJNR: 22, March 2001 STROKE AND TUMORS 457
determining changes in diffusion anisotropy when TEeff]). The field of view was 30 3 19 cm, and the matrix
lesions involve white matter tracts (17–21). size was 128 3 128. The section thickness was 7 mm, with a
3-mm intersection gap, and 11 to 17 axial sections were ob-
Some studies have shown that diffusion anisot- tained. The motion-probing gradients were applied sequentially
ropy in the white matter and the apparent diffusion in three orthogonal axes in the direction of the section select
coefficient change under pathologic conditions (17, (z), phase-encoding (x), and readout (y) gradients, with a b
22–26). As far as we know, however, there have factor of 1000 s/mm2, to generate three orthogonal axis dif-
been no reports evaluating changes in the anisot- fusion-weighted images (x, y, z). T2-weighted images without
ropy of white matter tracts in various disease states. motion-probing gradients (b 5 0 s/mm2) were also obtained.
Several investigators have examined the relation- The patient’s head was symmetrically positioned and fixed in
the head coil.
ship between involved and/or dysfunctional tracts
and diffusion anisotropy (17, 20, 24). The purposes
of this study were to compare diffusion anisotropy Neurologic Findings
in white matter tracts of patients with various types We reviewed each patient’s medical record for neurologic
of pathologic findings and to investigate the asso- findings at the time of MR imaging. We paid special attention
to motor deficits (hemiparesis), which were graded into four
ciation between anisotropy of the tracts and neu- categories: none (no hemiparesis), transient (hemiparesis that
rologic dysfunction. We chose supratentorial seg- disappeared before MR imaging study), slight-mild (hemipa-
ments of the corticospinal tract (the posterior limb resis but muscles capable of contracting against resistance),
of the internal capsule and the corona radiata) as a and moderate-severe (hemiparesis with muscles incapable of
target for investigation, and comparison was made contracting against resistance).
between patients with stroke and those with tumors
and between patients with and without hemiparesis. Evaluation of MR Images
Using both conventional MR and diffusion-weighted imag-
es, we evaluated the presence or absence of lesional involve-
Methods ment of the supratentorial segments of the corticospinal path-
Patients way, including the posterior limb of the internal capsule, the
corona radiata, and the cortical or subcortical region around
We retrospectively reviewed MR studies that included dif-
the central sulcus, including sensorimotor cortices.
fusion-weighted images from January 1998 to October 1998
and selected those patients with supratentorial tumors and
those with supratentorial cerebrovascular disease. We also se- Data Analysis for Diffusion Anisotropy
lected nine control patients who had undergone diffusion- The signal intensity (Si, i 5 x, y, z) on each diffusion-
weighted imaging during the same period. The inclusion cri- weighted image (x, y, z) is described by Si 5 S0exp(2bDi) (i
teria for the control patients were normal results of their 5 x, y, z), where S0 is the signal of the reference image and
neurologic examinations and MR imaging of the brain. The Di is the apparent diffusion coefficient in the ‘‘i’’ direction of
selected control patients had only minor complaints, such as the motion-probing gradient. We evaluated diffusion anisot-
headache, nausea, and dizziness. Patients with bilateral hemi- ropy according to the SD index (ASD) defined by the following
spheric neurologic deficits, involvement of bilateral cortico- formula (27):
spinal tracts, and infratentorial lesions were excluded from this
study. Patients with asymmetrical head positioning and those ASD 5 {[(Dx 2 DAV)2 1 (Dy 2 DAV)2
who moved during diffusion-weighted image acquisition were
also eliminated. 1 (Dz 2 DAV)2 ] / 6} 1/2 / DAV
Thirty-three patients and nine control patients constituted the
study, including 23 men and 19 women (age range, 8–81 years; where, DAV 5 (Dx 1 Dy 1 Dz) / 3.
mean age, 51 years). Eleven patients had tumors (three malig-
nant gliomas, two metastatic tumors, three low-grade gliomas, The three-orthogonal diffusion- and T2-weighted images (b
two brain abscesses, and one unknown nodular tumor), 16 had 5 0) were transferred to a workstation for image processing.
acute cerebral infarctions less than 2 weeks after ictus (range, ASD values were calculated on a pixel-by-pixel basis to gen-
0–14 days; mean, 3.4 days), and four had chronic cerebrovas- erate ASD map images using numerical computation software.
cular disease. Two patients who presented with transient is- For every case, we selected two or three sections in which
chemic attacks (hemiparesis) showed no MR abnormality. the posterior limb of the internal capsule or the corona radiata
was included. On each section, the rectangular regions of in-
terest (ROI) were defined in the posterior limb of the internal
Image Acquisition capsule or the corona radiata on both the affected side and the
All MR studies were conducted using a 1.5-T supercon- contralateral unaffected side. To define the ROI on these ana-
ducting system. The typical imaging protocol consisted of sag- tomic structures as accurately as possible, we used our origi-
ittal T1-weighted (400/14/1 [TR/TE/excitations]) spin-echo, nally developed software. Using this software, three different
axial T1-weighted (400/14/1) spin-echo, axial T2-weighted images of the same section, including the ASD map image, the
(4000–4300/105 [TR/TEeff]; echo train length, 10–12) fast DAV image, and a selected reference image, were displayed at
spin-echo, axial and/or coronal fluid-attenuated inversion re- the same time. When an ROI was defined on the reference
covery (10002/148 [TR/effective TE]; inversion time, 2200 image, the location of the ROI was shown on the other two
ms), and axial diffusion-weighted imaging sequences. For images simultaneously (Fig 1). Because the fiber tracts of the
some of the patients, contrast-enhanced T1-weighted (400/14/ posterior limb of the internal capsule and the corona radiata
1) sequences were additionally obtained. For these sequences, run in the craniocaudal direction, we used the Dz image as a
with the exception of the diffusion-weighted imaging sequenc- reference image. These anatomic structures were usually easily
es, the field of view was 20 to 22 cm, the matrix size was 256 identified on the Dz and ASD map images because of their
3 192, and the section thickness was 5 mm, with a 2.5-mm strong anisotropy, and the lesions were identified on the DAV
intersection gap. images in most cases. We also referred to the conventional MR
Diffusion-weighted images were obtained using multisection images and the three orthogonal diffusion-weighted images for
single-shot spin-echo echo-planar imaging (10000/98 [TR/ visual comparison.458 HIGANO AJNR: 22, March 2001
FIG 1. Screen of defining ROI. The DAV image (upper left), the ASD map image (lower left), and the Dz image (lower right) were displayed
on the screen, and the location of the defined ROI were shown on the three images simultaneously.
To standardize these ROI values, an asymmetry index (%) TABLE 1: Relationship between the degree of hemiparesis and the
of ASD, AI(ASD), between the affected side and the contralat- type of pathologic abnormality
eral side, was calculated according to the following equation:
MR-revealed
AI (ASD) 5 (ASD cnt ASD aff) / [(ASD cnt 1 ASD aff) / 2] Disease
3 100 Degree of No Acute Old
Hemiparesis N Lesion Infarct CVD Tumor
ASD aff and ASD cnt represent ASD values from the ROI of the
None 11 0 4 3 4
corticospinal tracts on the affected side and the corresponding
Transient 3 2 1 0 0
ROI on the contralateral side, respectively. In cases with hemi-
paresis, the responsible side for the hemiparesis was regarded Slight-mild 12 0 8 1 3
as the affected side. In cases with no paresis, the hemisphere Moderate-severe 7 0 3 0 4
having the main lesion was regarded as the affected side. In Total 33 2 16 4 11
control cases that had neither hemiparesis nor a lesion, the
index was calculated by supposing the left side to be the af- Note.—Data in the table represent the number of patients in each
fected side. The greater the AI(ASD) was, the greater was the category. N: Total number of each category.
reduction in anisotropy of the internal capsule or the corona
radiata on the affected side. The diffusion anisotropy may
change with age. Using the asymmetry index should minimize Results
the influence of age-related change.
These AI(ASD) values were compared among the various According to the medical records, 22 of 33 pa-
subgroups classified by the type of lesion that involved the tients had hemiparesis (Table 1). One patient with
ipsilateral corticospinal tract: control group, uninvolved tract, transient attacks of hemiparesis had acute infarction
acute infarction, old cerebrovascular disease, tumor edema, and in the frontal operculum.
tumor. We also compared the AI(ASD) for various degrees of Table 2 shows the relationship between the in-
hemiparesis, including control group, no paresis, transient pa- volved sites of the corticospinal pathway (posterior
resis, slight-mild paresis, and moderate-severe paresis. Statis-
tical analysis was conducted using analysis of variance with
limb of the internal capsule, the corona radiata, and
Scheffe’s post hoc test for multiple comparison. P values less the sensorimotor cortices) and the degree of hemi-
than .05 for multiple comparison were used to determine sig- paresis. In 21 cases, at least one segment of these
nificant differences. structures was involved. Nineteen of these patientsAJNR: 22, March 2001 STROKE AND TUMORS 459
TABLE 2: Relationship between the involved site of the cortico- that of the control, no paresis, and transient groups,
spinal pathway and the degree of hemiparesis but no significant statistical difference was noted.
As shown in Table 2, at least one segment of the
Degree of
Hemiparesis
corticospinal pathway from the sensorimotor cor-
tices to the posterior limb of the internal capsule
Mod- was involved in 21 cases. However, involvement of
Trans- Slight- erate- both the internal capsule and the corona radiata was
Involved Site N None ient mild severe noted in only four cases. In the remaining 17 cases,
No involvement (control) 9 9 0 0 0 either the internal capsule or the corona radiata or
No involvement 12 9 3 0 0 both on the affected hemisphere were not involved.
Sensory motor cortex (SMC) 3 0 0 3 0 We compared the mean AI(ASD) value of the nor-
Corona radiata (CR) 8 2 0 3 3 mal-appearing (uninvolved) internal capsule or co-
Internal capsule (IC) 2 0 0 2 0
SMC & CR 4 0 0 3 1
rona radiata between the 17 patients having some
IC & CR 4 0 0 1 3
involved segments of the corticospinal tract and the
other 21 patients with entirely intact corticospinal
Total 42 20 3 12 7 tracts (Fig 6). The mean AI(ASD) value of the
Note.—Data in the table represent the number of patients in each
group having involved segments tended to be larger
category. N: Total number of each category for involved site. than that of the group with the intact tract, although
a statistically significant difference was not noted.
The former group included 12 acute infarctions less
than 2 weeks old, four tumors, and one old cere-
brovascular disease. Eleven of these patients
showed slight-mild hemiparesis, four showed mod-
erate-severe hemiparesis (Fig 3), and two had no
paresis. All of them showed no MR finding of wal-
lerian degeneration.
Discussion
There are six major descending motor control
pathways: corticospinal tracts, corticobulbar tracts,
vestibulospinal tracts, reticulospinal tracts, rubro-
spinal tracts, and tectospinal tracts. The former two
pathways originate in the cerebral cortex, mainly in
the primary motor cortex, and descend through the
FIG 2. Mean and SD of AI(ASD) of the internal capsule or the corona radiata and the posterior limbs of the inter-
corona radiata involved by various types of lesions. Analysis of nal capsule supratentorially. They reach motor nu-
variance, F 5 39.6; P , .0001; Post hoc test (Scheffe); *, P 5 clei of cranial nerves and other brain stem sites
.05 as compared with the control group; **, P , .0001 as com- (corticobulbar fibers) or terminate to spinal cord
pared with both control and uninvolved groups.
motor neurons and interneurons (corticospinal fi-
bers) (28, 29). Therefore, supratentorial lesions in-
showed hemiparesis contralateral to the involved volving the primary motor cortex, corona radiata,
hemisphere. Two patients with involvement of the or posterior limb of the internal capsule often cause
corona radiata (one with old infarction and the motor deficits. We studied patients with supraten-
other with a low-grade astrocytoma) showed no torial lesions and found that 19 (90%) of 21 pa-
hemiparesis. tients with involvement of these structures had
Figure 2 shows the mean and SD of AI(ASD) of hemiparesis.
the internal capsule or the corona radiata involved The fibers descending through the internal cap-
by various lesions. All involved tracts had signifi- sule fan out as the corona radiata, just above the
cantly larger AI(ASD) than did uninvolved and con- internal capsule. The posterior limb of the internal
trol tracts (Figs 3 and 4). In addition, the mean capsule contains not only the corticospinal and cor-
AI(ASD) of the tracts involved by tumors (mass le- ticobulbar fibers but the fibers interconnecting ven-
sions) was significantly larger than that of tracts troanterior and ventrolateral nuclei of the thalamus
involved by the other three lesions. with the motor and premotor cortices and some of
Figure 5 shows the mean and SD of AI(ASD) for the somatosensory fibers (28, 29). This means that
each category, classified by the means of the degree the involvement of the corona radiata or the pos-
of hemiparesis. The mean AI(ASD) of the cases terior limb of the internal capsule does not always
with moderate-severe hemiparesis was significantly produce motor deficits. Two cases, each with a co-
larger than that of the remaining four groups, in- rona radiata lesion, did not show hemiparesis in
dicating more decreased diffusion anisotropy of the this series.
affected side. The mean AI(ASD) of the group of In the normal white matter, water molecular mo-
slight-mild hemiparesis showed a higher value than tion is unrestricted parallel to the tracts but is hin-460 HIGANO AJNR: 22, March 2001 FIG 3. Acute cerebral infarction of the right corona radiata with moderate-severe left hemiparesis. A, T2-weighted echo-planar image (b 5 0) shows an oval hyperintense lesion involving the right corona radiata. B, Apparent diffusion coefficient image shows a decreased diffusion coefficient in the lesion. C, In the ASD image, the diffusion anisotropy is also reduced. D, T2-weighted echo-planar image (10000/98 [TR/TEeff]) that includes the internal capsule shows no involvement of the right internal capsule, although high intensity spotty lesions were noted in the bilateral lentiform nuclei. E, Apparent diffusion coefficient image of the same section as that shown in D shows no definite abnormality in the internal capsule. F, ASD image shows decreased diffusion anisotropy in the posterior limb of the right internal capsule as compared with the left side. dered perpendicular to the tracts. This results in replace the fiber tracts with neoplastic tissue or ne- directional water diffusion or anisotropy. The dif- crotic tissue in the tumor. In our series, all the tu- fusion anisotropy may reflect the integrity of the mors that involved the internal capsule or the co- white matter structure. Therefore, impairment of rona radiata were high-grade gliomas. Our results water diffusion in the white matter may correlate indicate that the decrease in diffusion anisotropy of with the degree of the damage to its structure. In the white matter tracts varies for different types of our measurements, all involved internal capsules pathologic conditions. and coronae radiata showed significantly decreased The diffusion anisotropy of the internal capsule anisotropy in comparison with uninvolved ones. or the corona radiata in the affected hemisphere This reduction of anisotropy means decreased di- was correlated with the severity of hemiparesis. In- rectionality of the water molecular motion in the oue et al (18) evaluated the continuity of the py- white matter tracts. This phenomenon may be due ramidal tract in patients with brain tumors near the to loss of myelin, or replacement of myelinated fi- tract by using 3D anisotropy contrast MR images, bers with glial cells, or abnormal structures such as which were composed by combining color-coded tumors (24). We found that the diffusion anisotropy diffusion-weighted images with three orthogonal was significantly more impaired in the fiber tracts motion-probing gradients to delineate the fiber tra- involved by tumors than in those with infarction or jectory (19). On the 3D anisotropy contrast images, peritumoral edema. A possible explanation is that they could easily differentiate discontinuity of the a tumor may be more invasive and may completely tract due to impaired anisotropy from compression
AJNR: 22, March 2001 STROKE AND TUMORS 461
FIG 4. Glioblastoma involving the right corona radiata and basal ganglia with moderate-severe hemiparesis.
A, T2-weighted echo-planar image shows an irregular mass with marked perifocal edema involving the right corona radiata.
B, Apparent diffusion coefficient image shows an irregular mass with marked perifocal edema involving the right corona radiata.
C, In the ASD image, the diffusion anisotropy of the right corona radiata is hardly noted.
FIG 5. Mean and SD of AI(ASD) of the internal capsule or the
corona radiata for each degree of hemiparesis. Analysis of var-
iance, F 5 17.0; P , .0001; Post hoc test (Bonferroni); *, P ,
.0001 as compared with every other group.
FIG 6. Comparison of AI(ASD) value (mean and SD) of normal-
of the tract by the mass effect and showed good appearing internal capsule and corona radiata between the pa-
correlation between the findings and the pre- and tients with entirely intact corticospinal tract (Intact) and those hav-
postoperative motor functions. Karibe et al (20) ing some involved segments of the corticospinal tract (Involved).
studied patients with deep intracerebral hemorrhage
by use of anisotropic diffusion-weighted imaging
and evaluated the correlation between motor func- Wieshmann et al (24) measured the diffusion tensor
tion and corticospinal tract injury on diffusion- in the coronae radiata in patients with chronic
weighted images obtained at admission. Initial cor- hemiparesis caused by supratentorial lesions. In all
ticospinal tract injury was not correlated with the cases, the anisotropy was reduced in the coronae
motor impairment at admission but was closely radiata contralateral to the hemiparesis by more
correlated with motor impairment 1 month after on- than 3 SD compared with control participants, al-
set. They concluded that early evaluation of corti- though the significant difference was not noted be-
cospinal tract injury using diffusion-weighted im- tween patients with mild hemiparesis and those
aging could provide predictive value for motor with severe hemiparesis. In our results, however,
function outcome in patients with cerebral hemor- the diffusion anisotropy of the moderate-severe
rhage. In these two studies, the continuity of the hemiparesis group was significantly reduced as
fiber tracts on diffusion-weighted images was vi- compared with other groups. The study by Wiesh-
sually evaluated. In a quantitative evaluation, mann et al included only cases with chronic hemi-462 HIGANO AJNR: 22, March 2001
paresis, whereas we studied different types of path- recovered poorly showed distinct color fading in
ologic conditions, including tumors and acute and the pyramidal tract within 14 days after stroke.
chronic infarctions. These different constituents Our study had several limitations. We did not
may have affected the differing results. have software to obtain diffusion tensor imaging on
In the cases having some segments of the corti- our MR imaging unit, so we could not measure the
cospinal tract involved by pathologic abnormality, diffusion tensor exactly. The study was limited to
the diffusion anisotropy tended to be reduced not evaluate the diffusion anisotropy by using data with
only in the involved segments but also in the ap- three orthogonal diffusion gradients. Because most
parently uninvolved segments on the affected side. of the white matter fibers pass obliquely to the
Several investigators have reported similar find- magnet coordinates, the diffusion anisotropy cal-
ings. Pierpaoli et al (25) reported decreased an- culated by three-directional diffusion-weighted im-
isotropy in the midbrain and medulla oblongata of aging tends to be underestimated and the measured
the affected side by measuring the diffusion tensor values are also rotationally variant (15, 16). The
in patients with chronic supratentorial infarction. more accurate measurement of the diffusion an-
Wieshmann et al (24) showed the reduction of an- isotropy exactly along each fiber orientation re-
isotropy in the cerebral peduncle remote from su- quires diffusion tensor imaging, with at least nine
pratentorial lesions in patients with severe chronic different directional motion-probing gradients. To
hemiparesis. A possible explanation for such phe- minimize errors associated with our incomplete
nomena is wallerian degeneration of the fiber tracts measurements, we standardized the value using an
secondary to the supratentorial lesion. The waller- asymmetry index. However, such incomplete mea-
ian degeneration along the corticospinal tracts is surements of the diffusion anisotropy can lead to
usually detected at 4 weeks after cerebral infarction erroneous results, especially in some patients with
as a hypointense signal band on conventional T2- brain tumors in which the white matter fibers are
weighted images. It then becomes hyperintense af- distorted asymmetrically because of the mass ef-
ter 10 to 14 weeks and finally results in hemiatro- fect. This measurement error intrinsic to this study
phy of the brain stem (30). These two reports of might partly account for the markedly impaired an-
reduced anisotropy dealt with patients with chronic isotropy in the tracts involved by tumors as com-
disease. Our cases included patients with acute in- pared with that in tracts involved by other lesions.
farction of less than 2 weeks’ duration and no de- More exact evaluation by diffusion tensor mea-
tectable wallerian degeneration on standard MR
surement is required for further clarification. The
images. This shows that evaluation of the anisot-
number of cases in our study was too small to an-
ropy might detect wallerian degeneration or some
secondary degenerative change in white matter ear- alyze statistically the reduction of the diffusion an-
lier and with greater sensitivity than conventional isotropy between various types of pathologic con-
MR imaging. ditions involving the tracts and the degree of motor
There have been some reports regarding the re- impairment separately. Another limitation of our
lationship between wallerian degeneration and clin- study was that the control group consisted of pa-
ical findings. Wallerian degeneration of the pyra- tients, not of healthy volunteers. However, we care-
midal tracts was often found in patients with fully selected patients who did not have any neu-
capsular infarction, especially when associated with rologic signs and who had normal results of MR
motor deficit (31). Orita et al (32) measured an area imaging of the brain as the control patients. Despite
of wallerian degeneration in the pons on T2- these limitations, our results show some consisten-
weighted coronal images in patients with cerebro- cy with those of previous reports (24, 25, 32).
vascular disease of the internal capsule and con-
cluded that the area of wallerian degeneration was
related to the severity of the motor deficit. Watan- Conclusion
abe and Tashiro (33) and Sawlani et al (34) com-
pared the functional prognosis between patients The diffusion anisotropy in the posterior limb of
with and without wallerian degeneration and found the internal capsule or the corona radiata was sig-
that the presence of wallerian degeneration corre- nificantly reduced in cases with involvement to
lated well with persistent functional disability. these structures by infarction or tumor. This de-
Therefore, the measurement of the diffusion an- crease in anisotropy was more prominent in the
isotropy might help to predict the functional prog- tracts involved by tumors than in those involved by
nosis of patients earlier in the acute stage of in- infarction/edema and was correlated with the se-
farction. Igarashi et al (17) evaluated the change in verity of hemiparesis. The diffusion anisotropy
diffusion anisotropy associated with wallerian de- tended to be also impaired in normal-appearing fi-
generation of the pyramidal tracts in patients with ber tracts remote from the involved segment of the
supratentorial cerebrovascular accidents by use of corticospinal tract. Although more exact measure-
3D anisotropy contrast MR images. Patients ex- ments of the diffusion tensor are required, we think
amined during the acute stage who later recovered that evaluating diffusion anisotropy may provide
from hemiparesis had no visible changes on the 3D additional information relating to neurologic func-
anisotropy contrast images, whereas patients who tion and transneuronal effects.AJNR: 22, March 2001 STROKE AND TUMORS 463
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